1. Field of the Invention
The present invention relates to an improvement on a mixing element used in a static fluid mixer which mixes one or more kinds of fluids (liquids, gases, solids and mixtures of these) without a mechanically movable part, and also on a static fluid mixer using the mixing element.
Static fluid mixers of this kind are used in mixture, agitation, extraction, distillation, gas absorption, solution, stripping, emulsification, heat exchange, dispersion, particulate mixture and the like.
Further, static fluid mixers are used in many fields such as chemical industry, paper and pulp industry petrochemical industry, pharmaceutical industry, semiconductor industry, optical fiber manufacturing industry, energy industry and environment-related industry.
For example, a static fluid mixer is used as packing in an exhaust gas treatment apparatus of an absorption column method in which harmful substances in exhaust gas such as Hcl, NH3, NOx, SOx, Sicl4, SiHcl3, SiF4, CO2, Hg and dioxin undergo gas-liquid contact, in a dust removing apparatus which traps and collects SiO2, microparticles such as soot and dust in exhaust gas, and in a distillation apparatus. Further, a static fluid mixer is used as an apparatus for removing and collecting organic chlorine-based chemical compounds, ammonia (NH4+) and the like, in which discharged water undergoes stripping treatment and as an aeration treatment apparatus.
2. Description of the Related Art
Patent application for a mixing element and a static fluid mixer using the mixing element of related art have been made by the inventor, in which two right-twisted/left-twisted spiral blades are disposed in a passage tube. This static fluid mixer has an opening at its central part, and edges of right-twisted and left-twisted blades are alternately disposed at right angles to each other with space portions in between. Further, the twisting angles of these blades are 90° and 180°. Further, the production method of this static fluid mixer includes a process of dividing a passage tube into several parts in the longitudinal direction and joining two blades to an inner wall portion of the passage tube divided, and a process of joining together the divided surfaces of the passage tube (see Japanese Published Patent Application No. H5-168882, for example.).
Next, a production method of a mixing element in related art having blades which are provided inside a cylindrical passage tube to form a plurality of fluid passages that are continuous with an opening in between is explained. This mixing element is produced by constructing the passage tube and the blades separately, and then joining them together. Twisting angles of the mixing element are 90° and 180° (see Japanese Published Patent Application No. H7-284642, for example.). Further, the mixing element in related art is formed of a plurality of spiral blades provided in a passage tube, without the blades provided at the central part of the passage tube and inner cylindrical tubes are disposed at intervals in the part where the blades are not provided, so as to enhance mechanical strength. The rotation angles of the blades are 90° and 180°, or 30°, 45° and 135° (see Japanese Published Patent Application No. 2001-170476, for example.).
Further, in the mixing element are provided with an outer cylindrical tube, blades provided in the outer cylindrical tube, and inner cylindrical tubes provided at intervals so as to provide these blades in the outer cylindrical tube (see Japanese Published Patent Application No. 2001-187313, for example.).
And again, there is a duet for mixed fluid, in which a plurality of annular sleeves and a plurality of kinds of agitation wings of the same length are concentrically disposed at a mixture portion inside a main tube (see Japanese Published Patent Application No. H11-304067 and Japanese Published Patent Application No. H10-339396, for example). This duct for mixed fluid is not a technology which is within the realm of a fundamental mixture principle as a static fluid mixer by means of rightward and leftward rotation, convergence, turnover and division, but is a technology utilized by means of turbulence generated by agitation wings at a gas flow velocity of 20-34 m/s, in a flow concurrent with a mixture of gases, and also in a horizontal state. Also, regarding a plurality of agitation wings which are not spiral in form but are simply twisted, that are placed inside a short tube, since those agitation wings are not disposed evenly at regular intervals, fluid becomes channeling, which makes it difficult to produce a homogeneous mixed fluid, hence it is difficult to obtain the evenness of quality and the homogeneity of reaction. Further, for processing-related reasons, only a casting method can be employed to produce agitation wings having twists, particularly if made of metal. Thus, production costs become high. Also, the thickness of the agitation wings becomes greater. Further, in twisting agitation wings by means of a forging method, which is an inexpensive production method, cracks may occur in a metal plate material, so that it is difficult to produce agitation wings, and it may be impossible to produce a large diameter (1 m or more in diameter) in particular, because of the occurrence of cracks caused by a metal plate material expanding and contracting.
Also, an exhaust gas treatment system using a static mixer has been reported (see Japanese Published Patent Application No. H7-88319, for example).
Regarding a mixing element of related art, it is necessary due to the difficulty in terms of production by means of a forging method to enlarge the sectional area, that is to say the diameter, of an opening (the central part) in proportion to the diameter of a passage tube, as the diameter of the passage tube, through which fluid flows, becomes large. For that reason, there is a disadvantage that the effectiveness of mixture and agitation diminishes, because packing density lowers, and fluid flows directly in an opening, that is, a short circuit occurs. Further, in order to compensate for the decrease in the effectiveness of mixture and agitation, it is necessary to provide a large number of mixing elements in the longitudinal axial center direction, so that equipment costs become high, and pressure loss becomes high as well.
Furthermore, if a mixing element of a large diameter (internal diameter of 1 m or more) with a rotation angle of 180°, for example, is produced by means of a forging method, production may become impossible because of the occurrence of cracks in a plate material. Also, mold costs become high as well. Also, there is a disadvantage that mixture and agitation efficiency diminishes greatly, because the enlargement of the diameter of an opening causes fluid to short-circuit at the opening. Further, if the mixing element is used as packing in a distillation column in related art, replacement and provision of a mixing element may become impossible, hampered by the size of a manway formed with the diameter in the range of 400 mm to 700 mm.
Moreover, when a mixing element of a small rotation angle (for example, approximately 10°) of the present invention is produced and used, the mixing element can be provided and used as packing in a distillation column in related art, and improvement in packing density enables high performance and high productivity to be obtained.    [Patent Literature 1] Japanese Published Patent Application No. S58-128134    [Patent Literature 2] Japanese Published Patent Application No. H5-168882    [Patent Literature 3] Japanese Published Patent Application No. H7-80279    [Patent Literature 4] Japanese Published Patent Application No. H7-284642    [Patent Literature 5] Japanese Published Patent Application No. 2001-170476    [Patent Literature 6] Japanese Published Patent Application No. 2001-187313    [Patent Literature 7] Japanese Published Patent Application No. H11-304067    [Patent Literature 8] Japanese Published Patent Application No. H10-339396    [Patent Literature 9] Japanese Published Patent Application No. H7-88319    [Patent Literature 10] European Patent No. 0678329    [Patent Literature 11] U.S. Pat. No. 5,605,400    [Patent Literature 12] U.S. Pat. No. 6,431,528    [Non-patent Literature 1] S. J. Chen et al. “STATIC MIXING HANDBOOK” Chemical Research Institute, published in June 1973    [Non-patent Literature 2] Kiichiro Matsumura, Yasushi Morishima et al. “STATIC MIXER—FUNDAMENTALS AND APPLICATIONS”    Nikkan Kogyo Shimbun, Ltd., published on Sep. 30, 1981
As regards a mixing element and a static fluid mixer using the mixing element in related art, the larger the diameter of a mixing element becomes, the larger the diameter of the axial center portion becomes, due to production of blades by means of an inexpensive production method. Thus, since decrease in packing density makes mixture and agitation efficiency diminish, it is necessary to increase an amount of time when fluids are mixed and agitated. Therefore, columns such as an absorption column and a distillation column become greater in height, and so equipment costs become high. In addition, production and assembly become difficult as a diameter becomes large, and so mold costs become high as well. Further, the use of a mixing element in related art as packing in a distillation column in related art may have been impossible, because of the size of members such as a passage tube, blades and the like constituting the mixing element and performance-related aspects. Also, similarly, it may have been impossible to use a mixing element in related art as packing in an absorption column in related art for treating large gas volume.
Further, a large gas-liquid contact interfacial area, a high-performance liquid distribution function, and a wide operation control range under low pressure loss have been demanded regarding a distillation column using packing in related art (see Japanese Published Patent Application No. H7-80279, for example.). And again, as volume of exhaust gas generated from incinerators, vessels, power plants, rotary kilns and the like to be treated becomes large (for example, 0.1 million to 2 million Nm3/h), such advantages as high performance, less working space, less energy consumption and less cost of an absorption column used in exhaust gas treatment apparatuses are desired.